Dehumidifiers can be a great tool in reducing moisture levels in the crawl space but it is important to understand their benefits and their limitations.
How Does a Dehumidifier Work?
A dehumidifier reduces humidity in air by drawing moist air into the dehumidifier where it is cooled by a refrigerated coil and fan. Since colder air can hold less moisture, the water condenses and is then removed via a pump or gravity drain. The air in the dehumidifier is then reheated slightly and blown out. This process works best with higher ambient air temperature. As the air temperature is naturally colder, it becomes harder for the dehumidifier to cool the air further to remove and condense the moisture in the air.
Dehumidifiers are often described or classified by their water removal rate, for example 70 pints per day or 25 pints per day. This generally explains how powerful a dehumidifier is, yet it should be noted that this water removal is rated at 80 degrees F in temperature and 60% Relative Humidity. As either of these factors fall, the effectiveness of the dehumidifier is diminished. In other words, a dehumidifier is most powerful in warm and moist air. As air reduces its humidity and/or temperature decreases, there is a point of diminishing returns in what a dehumidifier can accomplish.
Operation of Dehumidifier
The operation of a dehumidifier costs a lot of money. Dehumidifiers have a high energy usage and will increase a homeowner’s electric bill. Power consumption will of course vary by model yet when a dehumidifier is the primary source for drying in a crawlspace it often runs quite frequently and uses a great deal of power. As an example, a very commonly used dehumidifier is rated at 580 watts of power (when at 80 degrees F and 60% RH). What does this mean for energy usage and cost to operate? A typical standalone dehumidifier in a crawlspace can conservatively be running twelve hours per day on average over the course of the year. The operation of this dehumidifier will cost approximately $305 per year in electricity costs (Based on the 12 cent per kilowatt/hour national average electricity cost). There are certainly scenarios where the dehumidifier runs even more frequently than the 12 hour per day example and many dehumidifiers run over 700 watts of power. So instead of $300 per year, the cost to operate can easily reach $600-$800 per year. This is a pretty significant annual expense to a homeowner. (As a comparison, a typical ATMOX System with 4 fans uses just 38 watts of power and may run fans approximately six hours per day on average over the course of the year. The operation of the ATMOX System at the same electricity cost would be approximately $10 per year.)
Range of Dehumidifier
Dehumidifiers with more power will be able to cover a larger space. But it may be important to supplement the dehumidifier with fans to increase air flow when the dehumidifier is running. Otherwise the drying action of the dehumidifier will have a difficult time reaching air from far corners of a crawlspace and at the same time overdrying wood directly around the dehumidifier. ATMOX recommends the use of dead space or joist mounted fans in these larger crawlspace setups.
Limitations of Dehumidifier
The greatest limitation of the dehumidifier is in cold temperatures. In colder climates or in the winter, the dehumidifier just does not have the ability to condense moisture out of the air by cooling it. While the dehumidifier attempts to reduce the humidity level, it will run and run with little measurable effect. A dehumidifier not designed for outdoor temperatures may also freeze up if trying to operate when it is too cold in the air.
Benefits of Dehumidifier
The dehumidifier can reduce moisture levels when the temperature remains reasonably high, such as in the summer time in most climates. In the summer time, it can be very effective tool as a drying action.
How ATMOX Uses a Dehumidifier
The ATMOX System uses a dehumidifier as a supplemental drying tool in certain crawlspaces or climates. The goal is to always use the most effective and most energy efficient drying tool. Throughout most of the year, drier outside air is available to improve the moisture levels in the crawl space. Using the fans to ventilate, the ATMOX System reduces moisture with little power usage and gets a balanced air flow throughout all areas of the crawlspace. In the summer months, temperature and humidity tend to peak and in some climates mother nature does not cooperate enough for the system to find “good, dry air” from the outside for a period of time. In these situations, when the crawlspace reaches a humidity range outside of the comfort zone of the system as set in the controls, the ATMOX system will activate the dehumidifier as its secondary drying tool until outside dry air is available again for proper ventilation.